Detection in liver tissue of AIH patients not only observed aggregation of CD4 + and CD8 + T cells overexpressed by immune checkpoint PD-1 and 4-1BB, but also found that PD-1 + CD8 + T cells were strongly associated with disease activity and degree of liver injury in AIH patients rather than PD-1 + CD4 + T cells [90]. Here, PDCD1 is linked to autoimmune hepatitis.